TUCSON, Ariz. -- After a year of struggling to re-learn how to walk and speak, U.S. Rep. Gabrielle Giffords confidently climbed the steps on an outdoor stage on Sunday and led a crowd of hundreds in the Pledge of Allegiance, her words ringing out on a cold Tucson night just one year after she survived a gunshot to the head.

The remembrance at the University of Arizona culminated a day of events, some filled with sadness and regret, others with hope and joy.

Many wept at an afternoon event as two 10-year-olds remembered their best friend, Christina-Taylor Green, who was killed in the Jan. 8, 2011 shooting, along with five others.

Some danced in celebration after Giffords' husband, former astronaut Mark Kelly, told the crowd at the candlelight vigil that the 13 survivors who emerged from the shooting showed that "alongside human frailty there is also strength."

And they chanted – "Gabby! Gabby! – when Giffords limped to the podium, and, after months of intensive speech therapy, recited the pledge with the audience, head held high and a smile on her face as she punched each word.

" ... with LIBERTY and JUSTICE for ALL!" the Democratic congresswoman shouted, almost defiantly.

The day included a church service that drew hundreds in the afternoon and a citywide bell-ringing at 10:11 a.m., the exact time a gunman started shooting at a Safeway political event on Jan. 8, 2011.

Suzi Hileman, who took her young friend and neighbor, 9-year-old Christina-Taylor Green, to meet Giffords that day, took the stage at the vigil and hugged Giffords, walking to the candle area, lighting one of 19 candles for all those killed and wounded, and mouthing "thank you" to the crowd.

Ron Barber, a Giffords staffer who was shot twice, helped lead events throughout the day, including the vigil. He woke up Sunday dreaming about Giffords, who was severely wounded, and Giffords staffer Gabe Zimmerman, who died.

"You have to think about the six people whose loved ones don't have them today," Barber said.

And Giffords, 41, who unexpectedly spoke Sunday after spending the past year in Houston undergoing intensive physical and speech therapy in a recovery that doctors and family have called miraculous.

"You made us so proud and happy when just months after your injury, you were in Congress casting your vote," said Dr. Peter Rhee, who treated Giffords at the hospital after she was shot. "We're so looking forward to having you back."

Doctors have said it would take many months to determine the lasting effects of her brain injury. The three-term congresswoman has four months to decide whether to seek re-election.

On Sunday, she smiled and nodded during the service, but didn't clap her hands. She walked with assistance, under the watchful eye of Kelly. Giffords and Kelly lit a candle together, and she rose to hug survivor Pam Simon.

"Even though it's a hard weekend for her and all of us, she wanted to be here with her community to remember," said Barber, who spent time with Giffords throughout the weekend. "She's sad, we're all sad, and she's glad to be home."

President Barack Obama called Giffords on Sunday to offer his support and tell her he and the first lady are keeping her, the families of those killed and the whole Tucson community in their thoughts and prayers, according to the White House. He said Giffords was an inspiration to all Americans.

Jared Lee Loughner has pleaded not guilty to 49 charges in the shooting. The 23-year-old, who has been diagnosed with bipolar disorder, is being forcibly medicated at a Missouri prison facility in an effort to make him mentally ready for trial.

In his speech at the candlelight vigil, Kelly referred to the pain that knowing that with adequate mental health care treatment for Loughner, the shooting may never have happened

"There's a reality that life is unpredictable, and that even in the best of times, our cherished friends, the good, the caring, the innocent among us, the closest and dearest people we know, can be taken from us," Kelly said.

The most poignant moment of the day came at an afternoon event at the University of Arizona. The two best friends of Christina-Taylor Green, who was born on Sept. 11, 2001, and was just 9 when she was shot and killed, spoke about their friend who went to the Safeway event with questions for her congresswoman she never got to ask.

"She wasn't afraid of boys or sports or anything," Serenity Hammrich said, wearing a black dress and standing with Jamie Stone on stage while many in the audience wept. "When she made student council, I was so happy for her. She believed it was important to help others to try to make a difference in the school and to put others first."

"I want everyone to understand that Christina was one in a million," Serenity said. "She was my best friend."

The Rev. Andrew Ross, spoke for shooting victim and his congregant Phyllis Schneck.

"I remember just shaking and as I shared with my congregation, my immediate response was anger, in fact rage, that someone would once again do this to a member of our flock," Ross said. "And so it's good for us to be honest and admit it's not easy remembering this day. We have to be honest about that."

The words of the 23rd Psalm brought comfort to some at an interfaith service at St. Augustine Cathedral on Sunday afternoon.

"Yeah, though I walk through the valley of the shadow of death, I will fear no evil," recited those gathered, including Arizona Gov. Jan Brewer. Relatives of the six dead walked solemnly down the aisle with a single red rose, placing the flowers in a vase in front of a picture of a heart.

"Even in the midst of this troubling year, the healing, the courage that we have experienced in our community – each one of us can notice how our cups overflow with the blessings of our lives," said Stephanie Aaron, Giffords' rabbi.

Throughout the day, the remembrance spilled out into the community. At the Safeway where the shooting erupted one year ago, about 30 people gathered at 10:11 a.m. to ring bells and to remember. Many bowed in prayer.

Gail Gardiner, 70, who lives about a mile away, tied a balloon Sunday that said, "Thinking of you," to a railing next to a memorial of the shooting that reads: "The Tucson Tragedy ... we shall never forget."

Albert Pesqueira, assistant fire chief for the Northwest Fire District in Tucson, was one of the first responders to the shooting. He came to the Safeway on Sunday to remember and to heal.

His most vivid memories from that day are the sounds of moaning and crying among shooting victims in the aftermath of the attack.

"I can still hear them," Pesqueira said. "We'll never be the same. We'll never be normal again because of what occurred."